1.5 The Theory of Plate Tectonics

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Vocabulary:

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Scientific theory-a well tested concept that explains a wide range of observation
Plates-the lithospere broken into separate sections
Plate tectonics-a geological theory that statesthe piecesof earth's lithosphere are in constant,slow motion,
driven by convection currents in the mantle
Faults-breaks in Earth's crust where rocks have slipped past each other
Divergent boundary-where two plates move apart, or diverge, usally occurs in the mid-ocean ridge
Transform boundary-where two plates slip past each other, moving in opposite directions
Rift valley-a deep valley that forms where two plates move apart
Collisons-when two plates converge,it's called a collision, it may bring together oceanic crust and continental crust,
or oceanic crust and oceanic crust, or continetal crust and continetal crust

Outline

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A Theory of Plate Motion

• the theory of plate tectonics explains the formation, movement, and subduction of Earth's plates
• pieces of Earth's lithosphere are in slow motion
• plates move by floating on the top of asthenosphere
• plates can do a lot:
  • collide
  • pull apart
  • grind past each other

Plate Boundaries

• three boundaries
  • transform boundaries
    • crust is neither created nor destroyed
  • divergent boundaries
    • when form on land, two of Earth's plates slide apart
  • convergent boundaries
    • when two plates collide, the density of the plates determines which one comes out on top
• oceanic crust is more dense than continental crust
• when two plates carrying continental crust collide, subduction doesn't take place

The Continent's Slow Dance

• plates move 2.5 centimeters per year
• 225 million years ago, pangaea began to break apart